NASA Says Venus May Have Supported Life Billions of Years Ago

NASA Says Venus May Have Supported Life Billions of Years Ago

Today, Venus and Earth don’t have a lot in common other than being about the same size and orbiting the same star. Venus has crushing atmospheric pressure and a surface temperature hot enough to melt lead. However, Venus might have been more Earth-like in the past. New simulations from NASA’s Goddard Institute for Space Studies show how that change may have taken place.

Venus is potentially in the habitable zone of the sun (opinions differ), so it could have liquid water on the surface. It doesn’t, though. Scientists have speculated that Venus’ water would have vaporized as it grew hotter thanks to a runaway greenhouse effect. The current surface temperature is over 700 degrees Fahrenheit (450 degrees Celsius), and the atmospheric pressure is almost 100 times higher than Earth’s. The planet’s surface is obscured by clouds of sulfuric acid rather than water vapor. Even robotic landers don’t last long under those conditions, and life as we know it has no chance.

Michael Way and Anthony Del Genio from Goddard produced five simulations of Venus, all of which show that the planet may have been habitable for 2-3 billion years. That changed from about 700 to 750 million years ago. Around that time, a massive resurfacing event released huge quantities of carbon dioxide that was previously locked under the surface. Three of the scenarios assumed ancient Venus had a topographical map similar to what we see today, including a deep water ocean of 310 meters and a shallower one 10 meters deep. The pair also ran a simulation with Earth’s topography and a 310-meter ocean and one version of Venus with a 158-meter body of water covering the entire surface.

The surface of Venus captured by a Soviet Venera probe.
The surface of Venus captured by a Soviet Venera probe.

According to the simulations, Venus should have been capable of hosting liquid water, and therefore life. Based on what we know of Earth, the early Venus would have had high levels of carbon dioxide that gradually became locked in silicate rocks. The simulations point to temperatures ranging from a pleasant 68 degrees Fahrenheit to a toasty 122 degrees Fahrenheit (20 to 50 degrees Celsius). To arrive at its current state, something must have changed on Venus around 700 million years ago. Way and Del Genio speculate that large magma flows may have freed up carbon dioxide from silicates but cooled before reaching the surface. This could have resulted in a barrier that prevented the gas from being reabsorbed.

We need more data on Venus to know how accurate these models are. It’s possible the planet cooled quickly and, like Earth, condensed water early on. However, it may also have been cycling larger amounts of carbon dioxide through the atmosphere for billions of years, preventing it from hosting water even before the major resurfacing event. Scientists may need to develop a heartier breed of robot that can spend more than a few minutes on the planet’s hellish surface.

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